The known CAD aperture card laser plotter allows CAD drawings to be produced directly on aperture cards by means of the laser beam. As the laser beam is to reproduce the lines of the drawing in a negative on the film, it has to be a reversal film in which white lines are formed by laser exposure. Such reversal films operate by the solarization principle. They are pre-exposed by the film manufacturer so that they receive a uniformly dark background having a density of about 1.8 or higher during full development. This high background density gives rise to problems during the production of paper enlargements. As the internationally standardised density of 35 mm negatives is between 0.9 and 1.2 for microfilming of drawings, the light intensity in the automatic enlargers is not sufficient constantly to reproduce fine lines with substantially denser negatives. The line width in the negative of the reversal film depends on the intensity of pre-exposure in addition to the concentration of the exposure beam. As pre-exposure takes place very intensively in reversal film for laser exposure, the edge regions of fine lines also rapidly become black during development so that too little or even no light of the automatic enlarger penetrates through the fine lines of few micrometers width onto the enlargement medium--paper or electrostatic printing drum.
This defect could be overcome by influencing the development process and, for example, developing the film less. The disadvantage arises here, however, that uniform development and therefore also density of the entire film surface cannot be achieved.